OBJECTIVES: Interferon Induction - (1) to define the mechanism of interferon induction using as a model a system in which a single (plus or minus) RNA D1-011 particle of vesicular stomatitis virus per cell induces a quantum yield of interferon and two or more particles per cell produce little or no interferon; (2) to define the molecular nature of the inducer moiety of Sindbis virus, its ts-mutants and early passage D1 particles; and (3) to define the mechanism that regulates which of two types of interferon dose (multiplicity of inducer)-response (interferon yield) curves is expressed during induction. Interferon action - to define further the inhibition of primary transcription by interferon action in some cell types infected with certain negative-strand viruses. Cell killing by viruses - to define the viral genes required for cell-killing by different viruses and to determine the nature and mode of action of the putative cell killing factor(s). Defective-interfering Particle Interference - (1) to obtain clonal populations of D1 particles in persistent infection - with an emphasis on "cell persistence" through interferon action and cell sparing. Intrinsic Interference - to determine the mechanism of intrinsic interference.